Hi Roger, I would expect that that shaft was too short, not to long.
We are talking about few milimetres to travel in length totally and even in
very, very few millimetres in difference what diff and hub flange distances differ.
Reasons can be weldings on the frame or strange setup with the shims.
If too long this will let the axle press outside when wheels are close to lower bumpstop.
All in all mostly a very small distance that will be accepted in the rubber bushings
maybe with strange driving behaviour but not with something to brake.
This misalignment is easy to detect when the axle is fitted.
My bet would be that axle was to short what is not noticed under normal driving conditions.
When driving over an obstacle the wheel can be pushed to the upper bumpstop and the
full way to travel of the cv-shaft is requiered.
If that is not enough the toothed end of the shaft is pushed out of the inner part of the cv-joint.
It is secured with a ring offering limited resistance against separation for inspection or renewing.
This pushed out shaft will have turned the inner part of the cv-joint, prohibiting that the shaft
can slide back where ist belongs. Than the wheels comes downward putting force on the shaft
until something brakes because the shaft now is much longer due to the mistake in the toothed end.
All that trouble started with ignoring the fitting instructions